Syncope: Causes and Symptoms

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Syncope is a medical term used to describe a brief episode of fainting or passing out. It generally occurs due to a decrease in the blood flow to the brain which may be due to low blood pressure or reduced efficiency of the heart in pumping out blood. This is a fairly common occurrence with up to 35% of individuals experiencing syncope at least once in their lifetime. It contributes to 3% of emergency visits and 1% of all hospital admissions.

Causes of Syncope

There are 3 general categories of syncope based on the underlying cause

  1. Neurally medicated syncope: This is the most common type of syncope with vasovagal syncope being the most frequent. This occurs from a nervous system reflex arc with a fall in heart rate and drop in blood pressure, leading to fainting. It may be provoked by intense emotions, pain, fear or anxiety.
  2. Orthostatic Hypotension: This is defined by a reduction in systolic blood pressure of 20 mmHg (millimetres of mercury) or reduction in diastolic blood pressure of 10 mmHg within 3 minutes of standing up. It occurs from dysfunction of the autonomic nervous system which is responsible for maintaining normal blood pressure with postural changes. Certain drugs, increasing age and several neurological disorders are associated with this type. The person experiences fainting on standing up.
  3. Cardiac Syncope: This refers to any situation where the fainting episode occurs due to decreased pumping of blood by the heart. This may occur due to arrhythmias (abnormal heart rhythm) or from structural heart diseases following heart attacks and heart valve disease leading to heart failure.

Symptoms of Syncope

  • Brief loss of consciousness followed by recovery within few minutes.
  • Fainting following exercise or eating.
  • Preceding symptoms (Presyncope)
    • Light headedness
    • Fatigue
    • Clouding of vision
    • Abnormal hearing or buzzing sensation
    • Palpitations or abnormal heartbeat

Evaluation of Syncope

Upon presentation, the history surrounding the episode of syncope is looked at with a detailed account from the patient and any eye witnesses of the fainting spell. A complete physical exam including a thorough neurological exam is performed to look for any deficits in function. Further tests are performed

  • Orthostatic blood pressure measurement: This is the measurement of blood pressure in the seated and standing postures to look for any abnormal fall in the pressure.
  • ECG (Electrocardiogram): This is done to look for any abnormal heart rhythms and can indicate if there has been an old or recent heart attack.
  • Echocardiogram: This is a test which uses an ultrasound to look at the heart and assess its function. The heart’s structure including its valves may be visualised and the cardiac output can also be assessed.
  • Complete blood count: This is done to look for anemia which may be a contributing factor to syncope
  • Blood glucose testing: Hypoglycemia can cause loss of consciousness and should be differentiated from syncope.
  • Tilt table testing: This test involves securely strapping the person to a tilt table and measuring blood pressure at different positions.
  • Autonomic Testing: This comprises several tests which are done to assess the autonomic nervous system of the body.

Management of Syncope

The management of syncope includes the following recommendations

  • Avoiding any stimuli known to provoke syncope
  • Adequate intake of fluids and salt to maintain blood volume and blood pressure
  • Isometric counterpressure maneuvers: These are limb maneuvers like leg crossing and arm tensing to increase blood pressures when the individuals experiences symptoms of presyncope.
  • Stopping any medications leading to orthostatic hypotension
  • Patient education for staged movements from sitting to standing int those with orthostatic hypotension
  • Management of arrhythmias: drugs, cardiac interventions and pacemakers are recommended based on specialist opinion.

Prognosis of Syncope

The vast majority of patients experiencing syncope may not have any recurrence. In those with recurrent episodes, a specialist’s opinion should be sought out. With specific therapy, individuals usually can live a normal life with control of symptoms.


  1. Roy Freeman, Syncope, Harrison’s Principles of Internal Medicine, 19th Edition
  2. Syncope (Fainting) [Internet] [cited 2018 Aug 7]